1. Field of the Invention
The present invention relates to a indexable end mill having a plurality of indexable inserts attached to the outer periphery of a shank and axially spaced at required intervals starting from the distal end of the shank.
2. Description of the Related Art
A variety of end mills have conventionally been utilized for grooving, corner milling, side milling and the like. Recently, indexable end mills have been adopted as a kind of such end mills. The indexable end mill is adapted for exchange of multiple indexable inserts attached to the outer periphery of the shank and axially spaced at required intervals starting from the distal end thereof.
More recently, the aforesaid indexable end mill has an arrangement generally shown in FIG. 1 for improvement of the cutting performance. More specifically, a shank 20 is formed with a plurality of right hand helical flutes 22 in the outer periphery thereof, each helical flute extending from the distal end of the shank 20 as inclined rearwardly in the direction of rotation of the shank and having a plurality of indexable inserts 10 sequentially attached thereto rearwardly with respect to the axis of the rotated shank and axially spaced at required intervals along the flute.
In the cutting of workpiece using such a indexable end mill, as shown in FIG. 2, the indexable end mill is rotated by a drive unit (not shown) while chips produced by outer-peripheral-side cutting edges of the indexable inserts are guided into the helical flutes 22 in the outer periphery 21 of the shank 20 so as to be discharged out of the flutes in conjunction with the rotation of the shank 20.
Unfortunately however, after guided into the aforesaid helical flutes 22 inclined at a required angle relative to the axis of the shank 20, the chips are moved in the helical flutes 22 due to the rotation of the shank 20, and then are caught and fused between the indexable inserts 10. Thus, the capability of discharging chips is reduced. Additionally, the caught chips build up in the helical flutes 22 to interfere with the rotation of the indexable end mill, resulting in an increased load on the indexable inserts 10 and shank 20. As a result, the breakage of the indexable inserts 20 or shank 20 occurs.
In case where a workpiece is subject to the cutting by means of the indexable end mill of the above structure, the indexable inserts 10 at the distal end of the shank 20 first hit the workpiece, successively followed by the rest so that the workpiece is processed.
However, if the indexable inserts 10 hit the workpiece in sequence of from that at the distal end of the shank 20 or that farthest from place where the indexable end mill is mounted to the drive unit, the indexable end mill suffers a greater vibration during the cutting operation and becomes incapable of performing a precise cutting work.
In recent attempts to solve these problems, a indexable end mill as shown in FIG. 3 has been proposed (see Japanese Examined Utility Model Publication No.6(1994)-18733). This end mill is arrange such that a plurality of indexable inserts 10 are sequentially attached to the outer periphery 21 of the shank 20 at forward places with respect to the axis of the rotated shank as axially spaced at required intervals starting from the distal end of the shank. On the other hand, the shank 20 is formed with helical flutes 22 for discharging chips produced by the indexable inserts 10, the flutes 22 being defined forwardly of the indexable inserts 10 in the direction of rotation of the shank and extended from the distal end of the shank as inclined forwardly in the direction of rotation of the shank.
In the indexable end mill of FIG. 3, the indexable inserts 10 are arranged on the outer periphery 21 of the shank 20 in a left hand helix starting from the distal end thereof, as forwardly shifted one after another with respect to the axis of the rotated shank. When the indexable end mill of this arrangement is mounted to and rotated by the drive unit for cutting a workpiece, the indexable inserts 10 closest to the drive unit first hit the workpiece, successively followed by the rest of the indexable inserts 10 whereby the workpiece is processed. As compared with the indexable end mill shown in FIG. 1, this indexable end mill suffers a reduced vibration during the cutting operation, thus allowed to perform the precise cutting work.
In the indexable end mills of FIGS. 1 and 3, however, the indexable inserts 10 are attached to the shank with their respective outer-peripheral-side cutting edges 11 inclined at a small angle with respect to the axis of the shank 20. In case where the workpiece is subject to the cutting by means of the outer cutting edges 11 of the indexable inserts 10 having a small inclination, a great cutting resistance is exerted on the respective outer cutting edges 11 of the indexable inserts 10. The great cutting resistance causes breakage of the cutting edge 11 or an impulsive sound during the cutting operation. In addition, the chips produced from the cutting are slow to be separated from the cutting edges and tend to accumulate in spaces in the helical flutes 22 and between the indexable inserts 10.
In the prior-art indexable end mills as shown in FIGS. 1 and 3, the indexable inserts 10 are generally mounted to the outer periphery 21 of the shank 20 by using screws 1 through mount holes 12 formed in the respective indexable inserts 10.
With the indexable inserts 10 mounted to the shank 20 by means of the screws 1, each exchange of indexable inserts 10 requires the screw 1 to be unscrewed before exchanging the indexable inserts 10. Such an exchange of indexable inserts is cumbersome and time consuming, resulting in a poor working efficiency.